A study, involving 371 patients with mild cognitive impairment, has found that those with depressive symptoms had higher levels of amyloid-beta, particularly in the frontal cortex and the anterior and posterior cingulate gyrus (both involved in mood disorders such as depression).
The findings suggest that late-life depression could be a major risk factor for developing Alzheimer's faster than others.
http://www.eurekalert.org/pub_releases/2014-06/sonm-dit060814.php
Brendel, M. et al. 2014. Subsyndromal late life depression is associated with amyloid accumulation in mild cognitive impairment. Presented at the Society of Nuclear Medicine and Molecular Imaging's 2014 Annual Meeting, June 7, 2014, St. Louis, Missouri.